Dr. William Lassek is an unlikely celebrity: He's a soft-spoken adjunct at the University of Pittsburgh's Department of Epidemiology. But he also co-authored a widely publicized recent study, "Waist-hip ratio and cognitive ability: Is gluteofemoral fat a privileged store of neurodevelopmental resources?" According to its findings, men prefer women with narrow waists and wider hips -- "low waist-hip ratios," in the jargon -- because the fat around a woman's hips is higher in omega-3 fatty acids, which improve brain function. The study found that when mothers have such physiques, they and their offspring score higher on cognitive tests. Those findings have been touted by the national and international press, which has pondered the evolutionary advantages of Jennifer Lopez and fashion models.
How did this study come about?
Waist-to-hip ratio is of great interest to evolutionary psychologists, who try to see if evolutionary ideas can explain human behavior. Many studies show that men prefer women with low waist-hip ratios. That's true across different cultures and ethnic groups. The traditional explanations are that such women have higher fertility, and are healthier. But we were exploring what other relationships there might be.
We got the idea that it might have to do with omega-3 fatty acids. Omega-3 isn't common in the diet, but it is found in the fat stored in a woman's hips and thighs. So it might be that women store the fat to help build the baby's brains.
Tell me about your methodology. People are probably wondering if you just went out looking for curvy women to give IQ tests ...
No. There are lots of medical databases out there. The National Health and Nutrition Survey is done periodically, and collects tons of data. We were able to look at [waist and hip measurements] in relationship to lots of other things.
If there are evolutionary advantages to voluptuousness, why does society prefer rail-thin supermodels?
Well, if you look at Playboy models, they are thin. They have very small waists. It's the waist size that makes the waist-hip ratio. The skinnier a woman is, the more likely she is to have a low waist-hip ratio.
Was Playboy a research tool?
I just look at the measurements. Playboy centerfolds are a convenient way to ask, "What are the characteristics of women that men find attractive?"
Did you think your findings would get so much publicity?
No. Why this attracted so much attention puzzles me. It's not like we tried to solicit it: There was no press release.
Well, it's reassuring to hear women shouldn't worry so much about weight on their hips.
Hip and thigh fat is good fat. Women shouldn't feel bad about having it. But there's lots of research showing that. Why would people be surprised? Compared to other animals, we have fat babies, fat women and big brains. It's not hard to see a connection.
... But maybe the message people are getting is that it's OK to be fat. That's not the right message. Generally, as weight increases, waist-hip ratio increase even faster. If you really want a low waist-hip ratio, you almost have to be skinny.
A Chicago Tribune editorial jokingly claimed the study provides "a scientific answer to the question, 'Why is J-Lo so hot?' Because males have a biological imperative to produce intelligent offspring, that's why."
Exactly. That summarizes it well.
The study has only been published online, and nothing happened for a week or so. I was on vacation when it exploded into public interest, and I missed out on the morning news shows. My colleague was in the rainforest --
Studying Amazon women?
No, no, birdwatching. But I got back and I had dozens of e-mails from reporters.
I'm interested in another topic that's going to be controversial, and [the publicity] is making me think about that. It's about how evolution has shaped the brains of men and women. Women have higher omega-3 levels than men, and even in the 18th and 19th centur[ies], people said women think faster than men. There may be a connection.
Do you worry about such research perpetuating stereotypes, or pigeonholing people based on biology?
It's definitely a concern. From the time of Aristotle, biological information has been used to stereotype. ... But if you compare the bodies of men and women, obviously, they are very different. It doesn't require a leap to think their brains might be different, too.
Freud believed that if we looked at where behavior comes from, it would give us power to control it. We could say, "I know I'm biologically disposed to do this, but it's something I don't want to do." If we deny such biases, I think we become more subject to them.
How have your colleagues reacted to the attention you've gotten?
I guess it piqued some interest. But I think the coverage is considered -- unscientific.
This [study] has made people think about the relationship between evolution and the mind. So [the publicity] might be beneficial. I've just been trying to understand why this idea attracted so much attention. The things people make popular -- it's not rational.
Maybe there's an evolutionary explanation?
I don't know. I'm sure you can think of celebrities whose popularity is puzzling. The source of popularity is an interesting question, but I wouldn't know how to investigate it.